The present invention relates to an end plate.
As disclosed in Japanese Laid-Open Patent Publication No. 2016-91845, a fuel cell mounted on a vehicle such as an automobile is equipped with an end plate that functions as a manifold for causing fluid, specifically, fuel gas, oxidation gas, and coolant to flow through the cell stack of the fuel cell. The fuel cell is cooled by coolant supplied to and discharged from the cell stack via the end plate, while generating power using fuel gas and oxidation gas supplied to and discharged from the cell stack via the end plate.
The end plate is shaped as a rectangle having a pair of horizontal long sides and a pair of vertical short sides. The end plate has an opposed surface facing an end in the cell stacking direction of the cell stack, a recess, which opens in the opposed surface and forms a flow path through which coolant flows. The recess extends in the horizontal direction along the opposed surface. The end plate also has ribs on the bottom surface of the recess. The ribs protrude to the opening position of the recess, are provided at intervals in the vertical direction, and are formed to extend in the horizontal direction.
The recess has an inlet, through which coolant flows in, at one end in the horizontal direction, and an outlet, through which the coolant flows out, at the other end in the horizontal direction. The outlet is located at a position higher than the inlet because if the outlet is located at a position lower than the inlet, the air in the coolant might stay in the flow path in the recess.
The opposed surface, the recess, and the ribs in the end plate are covered by a plastic layer. When the end plate is fixed to a case, which surrounds the cell stack, the portion of the plastic layer that covers the opposed surface and the portions of the plastic layer that cover the distal end faces in the protruding direction of the ribs contact the end in the cell stacking direction of the cell stack. In this case, the cell stack is pressed in the cell stacking direction by the opposed surface and the ribs, so that the favorable cell stacking structure of the cell stack is maintained.
At this time, the opening of the recess formed in the opposed surface of the end plate is closed by the end in the cell stacking direction of the cell stack. This forms the flow path, through which coolant flows, inside the recess. The portion between the inlet and the outlet in this flow path is partitioned by the ribs, which are provided at intervals in the vertical direction. The coolant flows in the horizontal direction through the portions in the flow path that are partitioned by the ribs. The coolant cools the end in the cell stacking direction of the cell stack.
The fluid in the flow path and the end plate are insulated from each other by a portion of the plastic layer that covers the inner surface of the recess and the outer surfaces of the ribs. The end plate and the cell stack are insulated from each other by the portion of the plastic layer that covers the opposed surface and the portions of the plastic layer that cover the distal end faces in the protruding direction of the ribs.
From the viewpoint of efficiently cooling the end in the cell stacking direction of the cell stack with the coolant flowing through the flow path in the recess of the end plate, the coolant preferably passes through the portions in the flow path that are partitioned by the ribs in a uniform manner.
However, in the flow path in the recess, since the outlet is located at a position higher than the inlet, the flow of the coolant from the inlet to the outlet tends to be directed upward. As a result, the coolant flows less smoothly in the lowest one of the portions partitioned by the ribs of the flow path than the other partitioned portions. Therefore, the portion of the end in the cell stacking direction of the cell stack that corresponds to the lowermost portion of the flow path in the recess cannot be easily cooled, resulting in uneven cooling of the end.